The present disclosure relates to an optical scanning device including a scanning lens for imaging a light beam on a surface to be scanned, and to an image forming apparatus using the optical scanning device.
A standard optical scanning device that is used in, for example, laser printers and copiers includes a light source that emits a laser beam, a polygon mirror that deflects the laser beam and causes the laser beam to scan the surface to be scanned, and a scanning lens that images the deflected laser beam on a peripheral surface (surface to be scanned) of a photoconductive drum. The lens power of the scanning lens changes according to a change in temperature. For example, when the environmental temperature of the optical scanning device rises, the lens power will decrease, and a magnification error of a broader scanning width will consequently occur. This magnification error causes the image quality to deteriorate.
Generally speaking, an optical scanning device includes a synchronizing sensor that detects a laser beam outside the range of the scanning width for determining the writing position of the scanning line. After the lapse of a fixed time after the synchronizing sensor detects a laser beam, writing on the surface to be scanned by the scanning line is started. Accordingly, even when the foregoing magnification error occurs, the writing position of the scanning line will be the home position during a normal temperature. Nevertheless, the write end position will be affected by the foregoing magnification error.
Known is an optical scanning device that rotates a reflecting mirror, in accordance with the environmental temperature, which guides a laser beam to the synchronizing sensor in order to suppress the magnification error.